1. Field
Aspects of the present disclosure relate to redox flow batteries, and more particularly, to redox flow batteries having high energy density and high charge and discharge efficiency.
2. Description of the Related Art
Secondary batteries are highly efficient energy storage systems widely used for small mobile phones and middle and large power storage devices. Specifically, secondary batteries are used as main core parts in semiconductor and liquid crystal devices, acoustic devices, and information and communication devices (such as mobile phones and laptops). More recently, they started to be used as power sources in hybrid cars.
Such power storage systems require a stable energy supply and a high energy conversion efficiency. Recently, redox flow batteries have come into the spotlight as secondary batteries having a large capacity and high durability, which are most suitable for large power storage systems.
Unlike other batteries, an active material of the redox flow batteries exists as ions in an aqueous state instead of a solid state, and the redox flow batteries use a mechanism of storing and generating electric energy according to oxidation/reduction reaction of each ion in a cathode and an anode.
In other words, the redox flow batteries include an electrolyte solution, wherein an active material of an electrode is dissolved in a solvent. The cathode is oxidized and the anode is reduced when the redox flow battery including a catholyte and an anolyte having different oxidation numbers is charged, and the electromotive force of the redox flow battery is determined by a difference between standard electrode potentials (E0) of a redox couple forming the catholyte and the anolyte. Meanwhile, the catholyte and anolyte are supplied from respective electrolyte solution tanks by a pump. The redox flow batteries simultaneously have a quick reaction rate during oxidation and reduction on the surfaces of the cathodes and anodes like general batteries, and have large capacity like fuel cells.